Research On The Path Planning Method Of Complex Structural Parts Based On CNC Plasma Additive Manufacturing

Wire and arc additive manufacturing is a rapid manufacturing technology that synchronously melts wires to form the metal part layer by layer on a substrate.Compared with traditional manufacturing methods,WAAM has several advantages including a simple device,short production cycle,high material utilization,low manufacturing cost,especially suitable for manufacturing largesize metal components with medium complex shape.The optimum process parameters of plasma arc additive manufacturing were determined by orthogonal experiment.By established predicted model can be obtained weld width and height for various welding parameters.The predicted height can be used for STL model layering algorithm,and the predicted width can be used for composite path planning algorithm.The influence of overlap distance on weld surface forming quality is analyzed.If the overlap distance is too large,the upper surface will be pit,and if the overlap distance is too small,the upper surface will become inclined plane.The optimal overlap distance of multi bead weld is determined.It was found that pores form in the sharp corner lap when the angle of the sharp corner is less than 58.65°,therefore,the sharp corner correction strategy is proposed to correct the sharp corner lap path.A composite path planning method combining the zigzag path with the contour offset path is proposed for the two-dimensional contour with complex geometric features.The composite path planning method overcomes the disadvantages of the single path planning method,and has the advantages of strong forming ability and high geometric reduction degree.The mathematical principles of the key problems are analyzed in the composite path planning method,such as the judging method of internal or external contour,the judging method of concave or convex point,the calculation method of offset point and the calculation method of intersection point coordinate.The overlap distance between the contour offset path and the zigzag path is optimized,which can effectively avoid the pores.In order to reduce the influence of arc starting and extinguishing on forming quality,a fast moving method is proposed that stopping wire feeding,not closing arc and welding current less than 80 A.The influence of the material shortage region on the forming accuracy of multi-layer multi-bead components was analyzed.The material shortage region results in a height difference between the edge height and the middle height of every deposited layer,and the height difference increases as more layers are added and the height of the component increases.Furthermore,the influence of the material shortage region gradually extends from the edge to the middle,such that the upper surface presents a circular shape.A mathematical model was established to determine the height difference based on the area of the material shortage region.When the height difference reaches the weld height,an edge compensation weld is added to eliminate the height difference.Two groups of experiments were carried out with different path planning methods and process parameters.The experimental results show that the height difference compensation method completely eliminates the influence of material shortage region on the forming accuracy of the component,and has high feasibility and applicability.The data format of STL model is analyzed,and ASCII format is selected for data reading and post-processing.According to the characteristics of large forming size but low accuracy in wire and arc additive manufacturing,the equal thickness layering algorithm is realized.A path planning software was developed that including STL model reading,weld size prediction,equal thickness slicing,composite path planning,G code export and GUI interface.The forming experiments are carried out of three groups of complex components.The forming quality of the components is better and the size reaches the expected goal.